Lactarius montanus (Hesler & A.H. Sm.) Montoya & Bandala

Barge, Edward G. & Cripps, Cathy L., 2016, New reports, phylogenetic analysis, and a key to Lactarius Pers. in the Greater Yellowstone Ecosystem informed by molecular data, MycoKeys 15, pp. 1-58 : 19-20

Taxon classification Fungi Russulales Russulaceae

7. Lactarius montanus (Hesler & A.H. Sm.) Montoya & Bandala Figure 9

Description.

Pileus 30-100 mm in diameter, convex to ± depressed–convex to infundibuliform, viscid, smooth, azonate to zonate, zones consisting of darker spots arranged concentrically, gray–brown to vinaceous–gray to violet–brown; margin straight to slightly incurved when young, becoming straight and ± wavy. KOH on pileus cuticle and stipe green. Lamellae adnate to subdecurrent, crowded to subdistant, cream, discoloring violet where damaged with rust brown stains also often present on older material. Stipe 30-70 × 10-30 mm, equal to clavate, smooth with light tomentum often present especially toward base, dry, white to light brown, discoloring violet and eventually rust brown where damaged, solid, becoming hollow. Context white, discoloring violet and eventually rust brown where damaged. Latex scarce to copious, white, staining tissue violet. Odor strongly resinous. Taste strongly resinous.

Basidiospores 7-10.5 × 6-8 µm, Q = 1.2-1.5, broadly ellipsoid to ellipsoid; ornamentation forming a broken to partial reticulum. Pleuromacrocystidia 50-90 × 5-10 µm scarce to scattered, fusoid–acuminate; apex acute to moniliform. Cheilomacrocystidia 30-55 × 4-9 µm, scarce, fusoid–acuminate; apex acute to moniliform.

Ecology and distribution.

Under conifers in western North America. In the GYE, it occurs in wet areas, often along streams in the montane spruce-fir and krummholz zones, possibly always in the presence of Picea engelmannii , summer and fall.

Specimens examined.

U.S.A. MONTANA: Madison County, Madison Range, Mirror Lake, swampy area under Abies lasiocarpa and Picea engelmannii . 3 Sept 2013, EB120-13 (MONT); Madison County, Tobacco Root Mountains, Branham Lakes, under Picea engelmannii and Salix planifolia , 31 Aug 2013, CLC3001 (MONT), under Picea engelmannii , 1 Sept 2014, EB0071-14 (MONT), EB0072-14 (MONT), EB0073-14 (MONT).

Discussion.

In western North America, similar species with violet-staining flesh include Lactarius pallescens Hesler & A.H. Sm., Lactarius californiensis Hesler & A.H. Sm., and Lactarius cordovaensis Hesler & A.H. Sm. Lactarius pallescens and Lactarius californiensis are generally more white overall in color, have a slightly acrid to acrid taste (not strongly resinous), and do not stain green in KOH. Lactarius cordovaensis has orange–tan lamellae when young, and possibly slightly smaller basidiospores (7.5-9.5 × 6.5-8 µm). Lactarius uvidus , a European species whose presence has not been confirmed molecularly for North America, typically has a lighter pileus, a bitter taste (not strongly resinous), and does not stain green in KOH. Previous reports of Lactarius uvidus from the GYE ( McKnight 1982) and the Central and Southern Rocky Mountains in general likely refer to Lactarius montanus . See comments under Lactarius aff. brunneoviolaceus and Lactarius pallidomarginatus for features differentiating Lactarius montanus from those taxa.